1. Field of the Invention
The present invention relates to a multi-colored synthetic resin sheet having an upper surface and a back surface wherein the boundary between adjacent colors is gradated on the surface and throughout a transversal cross-section of the sheet. This invention further relates to a multi-colored synthetic resin sheet which is formed by pouring, at least two differently colored polymerizable liquid materials into a polymerizing apparatus, such as an opposed belts-type-continuous sheet making apparatus, to effect polymerization and hardening.
2. Description of the Prior Art
Heretofore, multi-colored sheets having gradated boundary portions have been produced by first forming a sheet and then applying coating materials of different colors to the surface of the sheet. Coating can be effected by spraying, printing, coating, etc. or by applying a colored film to the surface of a sheet; wherein the film had previously been prepared by spraying, printing, coating, dyeing, etc.
However, these sheets prepared by overlaying a film onto a substrate are characterized by low permanence in that separation due to external forces or with lapse of time can be a problem. Moreover, when such sheets are subject to heat or stretching such as during molding, creases can occur between the colored film and the core sheet due to the differences in expansion coefficients; or the color of the stretched portion can be deteriorated resulting in a noticeable difference in color density between the stretched and unstretched portions, which can spoil the apperance of the products. A need therefore, continues to exist for a multi-colored synthetic sheet having at least two colors which can be molded or heated without the aforementioned disadvantages.